You're not gonna stocl floor with a stock frame, unless you trim it and that isnt the right way.
Now, you cant just go any amount you want with a stock floor. You can only go far nd then there comes a point where you can channel or do a 1-2" raised floor to get you down to the doors. I'm going rocker on my 79. I'm using 2x4x1/4" box tubing from the firewall back. Also you'll have to raise the tranny tunnel, lower the body mounts, smooth out the "hump" under the cab where your feet go. All of that to get a stock floor. So stock floor isnt technically a stock floor.
I'd personally widen the rear section of the frame for more choices in rear setups. As it is now, a parallel 4 link is about all that will work, but you can widen the rear and use a tri 4, wishbone 3, etc. (come on guys, lets not get into this whole parallel 4 thing again, b/c if you really wanna argue, then why are you guys using a panhard tht allows movement at the most extreme moments when you need a watts link to say you're using the best).
Tubular a-arms. I'd just wait till ART gets theirs out.
Also, to lay you need to section the engine crossmember 1.5" b/c it hangs so damn low.